As conventional punch presses for selecting tools, two types punch presses are known, i.e., a type I in which a striker is fixed and a tool placed on a turret moves, and a type II in which the striker moves and the tool is fixed.
The prior art in type I is an example of a turret punch press in which a tool is placed on a rotation turret. Japanese Utility Model Publication No. H7-47140 discloses a method in which a single striker which straightforwardly moves selectively strikes two tools. That is, rotation positioning of a turret and straightforward movement of the striker are combined to finally select a tool.
It can be said that the prior art of type II is inferior in stability of tool position, and working precision such as a size of a machining device (height of productivity per installation area). In a striker mechanism as one example of the type II, a striker holder having a plurality of strikers which respectively strike heads of punches is provided above a plurality of tools (punches) set in the punch holder, and a ram is provided above the striker holder such that the ram can reciprocate in longitudinal direction and lateral direction (X-axis direction and Y-axis direction).
When the striker strikes the punch, the ram itself moves in the X-axis direction and the Y-axis direction to select a desired punch, the punch is positioned above the striker on the punch and then, the punch is lowered in the vertical direction (Z-axis direction), the striker strikes to carry out the punching working.
However, the prior art of the type I is based on index of the tools by rotation turret, and this technique has a problem in precision when a tool hole into which the tool is mounted is worked into a turret. This does not cause a problem in a general sheet metal working which is carried out by a conventional turret punch press, but if a product working having the same extremely high precision as that required for integrally forming thin plate by a press machine in electronic component industry is carried out by a punch press, it is required that distances between rotation centers of turrets and centers of tool holes are the same with high precision, but the working in a producing process of current turrets is extremely difficult operation, and even if it is possible, the cost is increased. That is, it is not preferable for high precision working to use a rotation member such as a turret for positioning. Further, there is a limit for positioning and stopping precision and positioning speed of the heavy rotation turret in which a tool is disposed. In Japanese Utility Model Publication No. H7-47140, in order to enhance the yield, two rotation positioning operations of a turret and a rotation cylinder which rotates in the turret are required, and it becomes more difficult to enhance the precision.
In the prior art of the type II, the ram strikes the punch, endures a high load, has a vertically driving mechanism, and if the mechanism is moved in the X-axis direction and Y-axis direction, there are problems that a guiding device and driving mechanism required for moving the ram becomes complicated, and volumes and costs thereof are increased, and energy consumption is also increased.
The present invention has been achieved with a view of the problems of the prior art, and it is an object of the invention to provide a punch press for a thin plate capable of precise working.